1. Field of the Invention
The following description relates to data reproduction using a viterbi decoder, and more particularly, to a data reproduction apparatus and method capable of accurately determining a level value of a viterbi decoder, and a computer-readable recording medium having recorded thereon a program to implement the data reproduction method.
2. Description of the Related Art
An apparatus for reproducing data from a recording medium (such as a disc) performs a binarization process to convert a radio frequency (RF) signal read from the disc into a binary signal. During the binarization process, a conventional data reproduction apparatus uses a viterbi decoder in order to obtain the binary signal with minimal errors.
However, for an optimal operation of the viterbi decoder, an initial level value of the viterbi decoder must be appropriately set for a channel characteristic and a phase-locked loop (PLL) clock in the data reproduction apparatus must operate normally. The normal operation of the PLL clock indicates that the operating frequency of the data reproduction apparatus is in a stable state.
If the initial level value of the viterbi decoder is not appropriate for the channel characteristic or the PLL clock does not operate normally, a binary signal is output from the viterbi decoder with an error. Accordingly, an erroneous reproduction signal is output from the data reproduction apparatus. A data reproduction apparatus that reproduces data from a high-density disc is particularly susceptible to such an error occurring.
Thus, if the PLL clock operates normally, the conventional data reproduction apparatus determines the initial level value of the viterbi decoder appropriate for the channel characteristic and binarizes an input signal while updating the level value of the viterbi decoder for the input signal. Thus, unless the PLL clock operates normally, the conventional data reproduction apparatus cannot determine the initial level value of the viterbi decoder.
Conventionally, when the PLL clock does not operate normally, the data reproduction apparatus binarizes an input signal using a preset initial level value of the viterbi decoder. However, if the preset initial level value of the viterbi decoder is not suitable for a channel characteristic, a binary signal is output from the viterbi decoder with an error. As a result, an erroneous reproduction signal from the data reproduction apparatus is output.